2 files changed, 11 insertions, 1 deletions
diff --git a/NEWS b/NEWS
index 369087b..57d2f52 100644
--- a/NEWS
+++ b/NEWS
@@ -11,6 +11,9 @@ Version 0.17, released UNRELEASED
   yarn output, such as CI systems, and get the timings differently
   from what would happen on a terminal.
 
+* The `--require-assumptions` option has been added to tell Yarn to
+  treat failing ASSUMPTIONS steps as errors.
+
 Version 0.16, released 2015-06-30
 ---------------------------------
 
diff --git a/yarn b/yarn
index 02bec29..fdfc695 100755
--- a/yarn
+++ b/yarn
@@ -84,6 +84,10 @@ class YarnRunner(cliapp.Application):
             'allow scenarios to reference steps that do not exist, '
             'by warning about them, but otherwise ignoring the scenarios')
 
+        self.settings.boolean(
+            ['require-assumptions'],
+            'require ASSUMING to always pass')
+
     def stdout(self, msg):
         self.output.write(msg)
         self.output.flush()
@@ -338,7 +342,10 @@ class YarnRunner(cliapp.Application):
             step_number += 1
             self.snapshot_datadir(
                 tempdir, datadir, scenario, step_number, step)
-            if exit != 0:
+            if self.settings['require-assumptions'] and exit != 0:
+                ok = False
+                break
+            elif exit != 0:
                 self.ts.notify(
                     'Skipping "%s" because "%s %s" failed' %
                     (scenario.name, step.what, step.text))